Antenna arrays hold great promise for bandwidth-efficient communication over wireless channels. Past studies have indicated a linear increase in capacity with the number of antennas. However, the research on multiple input, multiple output (MIMO) wireless communication systems was initially performed in rich multi-path environments and there is growing evidence that physical wireless channels exhibit a sparse structure even using relatively small antenna dimensions. The two main characteristics of fading spatial multi-path channels from a communication theoretic viewpoint are the capacity and the diversity afforded by the scattering environment. Two key factors affect the capacity: the number of parallel channels and the level of diversity associated with each parallel channel. The capacity and diversity of the spatial multi-path channel are determined by the richness (or sparseness) of multi-path.
Antennas have historically been viewed as static and passive devices with time-constant characteristics. After finalizing an antenna design, its operational characteristics remain essentially unchanged during system use. Technological advances in reconfigurable antenna arrays, however, are enabling new wireless communication devices in which the array configuration can be adapted to changes in the communication environment. Thus, understanding the impact of reconfigurable arrays on MIMO capacity and developing strategies for sensing and adapting to the environment is of significant interest. Thus, what is needed is a method of determining an antenna spacing in a reconfigurable antenna array that supports increased capacity based on the sensed multi-path environment. What is additionally needed is a method that supports increased capacity over the entire operational signal-to-noise ratio (SNR) range.